can a vlookup show a value based on if previous step is x or y

Help urgently required.

I created spreadsheet (see attached) and after doing all the work, someone decide extra data was needed
The spreadsheet is a selection chart for different product configuration, and indicates prices when certain configurations are shown.
My problem is i have a selection choice on worksheetCPB5800 CELL B23[information on worksheetCPS1]. This affects cost of measuring range of ROW23. [worksheetCPS3].
If I could program, I would expect CELL27 to have a function:
fx= IF B23=S, THEN E27=VLOOKUP(B27'CPS3'!A1:D5,3,FALSE, ELSE E27=VLOOKUP(B27'CPS3'!A1:D5,4,FALSE

(i.e. it chooses a different colum to collect data.)

Can anyone suggest a way I can achieve what I am looking for?

Thanks for everybodys help in advance

Dave